Reland "[Perfect Negotiation] Implement non-racy version of SetLocalDescription."
This is a reland of d4089cae47334a4228b69d6bb23f2e49ebb7496e
with the following fix:
Invoke MaybeStartGathering as the last step of DoSetLocalDescription.
This ensures that candidates and onicegatheringstatechange does not
happen before SLD is resolved. This is important for passing
external/wpt/webrtc/RTCPeerConnection-iceGatheringState.html.
Original change's description:
> [Perfect Negotiation] Implement non-racy version of SetLocalDescription.
>
> BACKGROUND
>
> When SLD is invoked with SetSessionDescriptionObserver, the observer is
> called by posting a message back to the execution thread, delaying the
> call. This delay is "artificial" - it's not necessary; the operation is
> already complete. It's a post from the signaling thread to the signaling
> thread. The rationale for the post was to avoid the observer making
> recursive calls back into the PeerConnection. The problem with this is
> that by the time the observer is called, the PeerConnection could
> already have executed other operations and modified its states.
>
> This causes the referenced bug: one can have a race where SLD is
> resolved "too late" (after a pending SRD is executed) and the signaling
> state observed when SLD resolves doesn't make sense.
>
> When implementing Unified Plan, we fixed similar issues for SRD by
> adding a version that takes SetRemoteDescriptionObserverInterface as
> argument instead of SetSessionDescriptionObserver. The new version did
> not have the delay. The old version had to be kept around not to break
> downstream projects that had dependencies both on he delay and on
> allowing the PC to be destroyed midst-operation without informing its
> observers.
>
> THIS CL
>
> This does the old SRD fix for SLD as well: A new observer interface is
> added, SetLocalDescriptionObserverInterface, and
> PeerConnection::SetLocalDescription() is overloaded. If you call it with
> the old observer, you get the delay, but if you call it with the new
> observer, you don't get a delay.
>
> - SetLocalDescriptionObserverInterface is added.
> - SetLocalDescription is overloaded.
> - The adapter for SetSessionDescriptionObserver that causes the delay
> previously only used for SRD is updated to handle both SLD and SRD.
> - FakeSetLocalDescriptionObserver is added and
> MockSetRemoteDescriptionObserver is renamed "Fake...".
>
> Bug: chromium:1071733
> Change-Id: I920368e648bede481058ac22f5b8794752a220b3
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/179100
> Commit-Queue: Henrik Boström <hbos@webrtc.org>
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31798}
TBR=hta@webrtc.org
Bug: chromium:1071733
Change-Id: Ic6e8d96afa1c19604762f373716c08dbfa9d178c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180481
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31804}
diff --git a/api/peer_connection_interface.h b/api/peer_connection_interface.h
index fd4d2df..52d0d87 100644
--- a/api/peer_connection_interface.h
+++ b/api/peer_connection_interface.h
@@ -97,6 +97,7 @@
#include "api/rtp_sender_interface.h"
#include "api/rtp_transceiver_interface.h"
#include "api/sctp_transport_interface.h"
+#include "api/set_local_description_observer_interface.h"
#include "api/set_remote_description_observer_interface.h"
#include "api/stats/rtc_stats_collector_callback.h"
#include "api/stats_types.h"
@@ -947,26 +948,56 @@
const RTCOfferAnswerOptions& options) = 0;
// Sets the local session description.
- // The PeerConnection takes the ownership of |desc| even if it fails.
- // The |observer| callback will be called when done.
- // TODO(deadbeef): Change |desc| to be a unique_ptr, to make it clear
- // that this method always takes ownership of it.
+ //
+ // According to spec, the local session description MUST be the same as was
+ // returned by CreateOffer() or CreateAnswer() or else the operation should
+ // fail. Our implementation however allows some amount of "SDP munging", but
+ // please note that this is HIGHLY DISCOURAGED. If you do not intent to munge
+ // SDP, the method below that doesn't take |desc| as an argument will create
+ // the offer or answer for you.
+ //
+ // The observer is invoked as soon as the operation completes, which could be
+ // before or after the SetLocalDescription() method has exited.
+ virtual void SetLocalDescription(
+ std::unique_ptr<SessionDescriptionInterface> desc,
+ rtc::scoped_refptr<SetLocalDescriptionObserverInterface> observer) {}
+ // Creates an offer or answer (depending on current signaling state) and sets
+ // it as the local session description.
+ //
+ // The observer is invoked as soon as the operation completes, which could be
+ // before or after the SetLocalDescription() method has exited.
+ virtual void SetLocalDescription(
+ rtc::scoped_refptr<SetLocalDescriptionObserverInterface> observer) {}
+ // Like SetLocalDescription() above, but the observer is invoked with a delay
+ // after the operation completes. This helps avoid recursive calls by the
+ // observer but also makes it possible for states to change in-between the
+ // operation completing and the observer getting called. This makes them racy
+ // for synchronizing peer connection states to the application.
+ // TODO(https://crbug.com/webrtc/11798): Delete these methods in favor of the
+ // ones taking SetLocalDescriptionObserverInterface as argument.
virtual void SetLocalDescription(SetSessionDescriptionObserver* observer,
SessionDescriptionInterface* desc) = 0;
- // Implicitly creates an offer or answer (depending on the current signaling
- // state) and performs SetLocalDescription() with the newly generated session
- // description.
- // TODO(hbos): Make pure virtual when implemented by downstream projects.
virtual void SetLocalDescription(SetSessionDescriptionObserver* observer) {}
+
// Sets the remote session description.
- // The PeerConnection takes the ownership of |desc| even if it fails.
- // The |observer| callback will be called when done.
- // TODO(hbos): Remove when Chrome implements the new signature.
- virtual void SetRemoteDescription(SetSessionDescriptionObserver* observer,
- SessionDescriptionInterface* desc) {}
+ //
+ // (Unlike "SDP munging" before SetLocalDescription(), modifying a remote
+ // offer or answer is allowed by the spec.)
+ //
+ // The observer is invoked as soon as the operation completes, which could be
+ // before or after the SetRemoteDescription() method has exited.
virtual void SetRemoteDescription(
std::unique_ptr<SessionDescriptionInterface> desc,
rtc::scoped_refptr<SetRemoteDescriptionObserverInterface> observer) = 0;
+ // Like SetRemoteDescription() above, but the observer is invoked with a delay
+ // after the operation completes. This helps avoid recursive calls by the
+ // observer but also makes it possible for states to change in-between the
+ // operation completing and the observer getting called. This makes them racy
+ // for synchronizing peer connection states to the application.
+ // TODO(https://crbug.com/webrtc/11798): Delete this method in favor of the
+ // ones taking SetRemoteDescriptionObserverInterface as argument.
+ virtual void SetRemoteDescription(SetSessionDescriptionObserver* observer,
+ SessionDescriptionInterface* desc) {}
virtual PeerConnectionInterface::RTCConfiguration GetConfiguration() = 0;